High arsenic(As)and chromium(Cr)concentrations are currently receiving attention because of their negative effects on the environment and human health.Microorganisms inhabiting contaminated environments have developed...High arsenic(As)and chromium(Cr)concentrations are currently receiving attention because of their negative effects on the environment and human health.Microorganisms inhabiting contaminated environments have developed resistance mechanisms against the toxicity of these pollutants.Indeed,members of the bacterial genus Micrococcus have been isolated from different toxic metal-contaminated environments;however,knowledge concerning its resistance mechanisms to As and Cr toxicity remains limited.Micrococcus luteus strains(An24,Mh,NE2TL6,and NE2TTS4)were isolated from the endosphere and soil of two heavy metal-contaminated sites in Mexico to identify differences in the resistance mechanisms by the M.luteus group.The strains were resistant to As(As^(3+)and As^(5+)),chromate,dichromate,cobalt,copper,nickel,and zinc.Genome analysis indicated that the heavy metal-resistant strains(An24,Mh,NE2TL6,and NE2TTS4)could be assigned to the M.luteus group and had more heavy metal-resistant genes(transporters,chaperones,and enzymes)compared to reference strains of the M.luteus group,M.luteus NCTC 2665^(T)and Micrococcus endophyticus JCM 16951^(T).The resistant bacteria were able to biotransform As^(3+)and As^(5+)through a carbon source-dependent mechanism.The biotransformation of As5+was potentially carried out in the cytoplasm through a thioredoxin-dependent pathway,which may be coupled with biosorption.A qualitative analysis of organic acids(OAs)identified a change in the OA profile of the metal-resistant strains that was As-or Cr-dependent.Our genomic and phenotypic findings suggest that the four M.luteus group strains evaluated in the current study have developed resistance mechanisms that may enable their survival in contaminated sites.展开更多
基金?nancially supported by the Instituto Politécnico Nacional (IPN),Mexico (Nos.SIP20170544,SIP20180115,SIP20196674,SIP20196729,SIP20200229,and SIP20200310)Ivan Arroyo-Herrera and Joseph Guevara-Luna received grant-aided support from Consejo Nacional de Ciencia y Tecnología (CONACyT) and Beca de Estímulo Institucional de Formación de Investigadores(BEIFI),Mexico+2 种基金Rafael Bustamante-Brito and Erika Y.Tapia-García received grant-aided support from CONA-CyTPaulina Estrada-de los Santos,En Tao Wang,and María Soledad Vásquez-Murrieta received grant-aided support from Comisión de Operación y Fomento de Actividades Académicas-IPN,Estímulos al Desempe?o de los Investigadores-IPN,and Sistema Nacional de Investigadores(SNI)-CONACyT,MexicoBrenda Román-Ponce received grant-aided support from SNI-CONACyT
文摘High arsenic(As)and chromium(Cr)concentrations are currently receiving attention because of their negative effects on the environment and human health.Microorganisms inhabiting contaminated environments have developed resistance mechanisms against the toxicity of these pollutants.Indeed,members of the bacterial genus Micrococcus have been isolated from different toxic metal-contaminated environments;however,knowledge concerning its resistance mechanisms to As and Cr toxicity remains limited.Micrococcus luteus strains(An24,Mh,NE2TL6,and NE2TTS4)were isolated from the endosphere and soil of two heavy metal-contaminated sites in Mexico to identify differences in the resistance mechanisms by the M.luteus group.The strains were resistant to As(As^(3+)and As^(5+)),chromate,dichromate,cobalt,copper,nickel,and zinc.Genome analysis indicated that the heavy metal-resistant strains(An24,Mh,NE2TL6,and NE2TTS4)could be assigned to the M.luteus group and had more heavy metal-resistant genes(transporters,chaperones,and enzymes)compared to reference strains of the M.luteus group,M.luteus NCTC 2665^(T)and Micrococcus endophyticus JCM 16951^(T).The resistant bacteria were able to biotransform As^(3+)and As^(5+)through a carbon source-dependent mechanism.The biotransformation of As5+was potentially carried out in the cytoplasm through a thioredoxin-dependent pathway,which may be coupled with biosorption.A qualitative analysis of organic acids(OAs)identified a change in the OA profile of the metal-resistant strains that was As-or Cr-dependent.Our genomic and phenotypic findings suggest that the four M.luteus group strains evaluated in the current study have developed resistance mechanisms that may enable their survival in contaminated sites.
